I really liked how deliberate the detail was of the whole hangover bit. It made her reaction once the potion kicked in that much more snapping and jarring (the "You!"). Really effective.

I also started to feel badly for Sirius towards the end of this, and it painted Hermione in a more imperfect light in these circumstances. Young Sirius is getting some nice character development happening here, and I can't wait to find out more of his actual personality.